EP0239563A1 - Measurement transducer - Google Patents

Measurement transducer Download PDF

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Publication number
EP0239563A1
EP0239563A1 EP87890054A EP87890054A EP0239563A1 EP 0239563 A1 EP0239563 A1 EP 0239563A1 EP 87890054 A EP87890054 A EP 87890054A EP 87890054 A EP87890054 A EP 87890054A EP 0239563 A1 EP0239563 A1 EP 0239563A1
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EP
European Patent Office
Prior art keywords
support body
hollow profile
transducer
profile
concrete
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EP87890054A
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German (de)
French (fr)
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EP0239563B1 (en
Inventor
Klaus Dipl.-Ing. Rabensteiner
Peter Dipl.-Ing. Dr. Schubert
Johann Dipl.-Ing. Dr. Golser
Georg Dipl.-Ing. Dr. Feder
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Hackl Erich Dipl-Ing
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Hackl Erich Dipl-Ing
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Publication of EP0239563A1 publication Critical patent/EP0239563A1/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
    • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
    • G01L1/2206—Special supports with preselected places to mount the resistance strain gauges; Mounting of supports
    • G01L1/2218—Special supports with preselected places to mount the resistance strain gauges; Mounting of supports the supports being of the column type, e.g. cylindric, adapted for measuring a force along a single direction
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge

Definitions

  • the invention relates to a transducer, consisting of a straight support body which can be axially stressed by the deformation of the measurement object surrounding it and of a casing surrounding the support body, and of at least 2 rigid transverse elements connected to the support bodies.
  • a transducer consisting of a straight support body which can be axially stressed by the deformation of the measurement object surrounding it and of a casing surrounding the support body, and of at least 2 rigid transverse elements connected to the support bodies.
  • strain gauges were constructed with a hollow profile as a deformation body, in which the cross-sectional area defined by the outer contour of the hollow profile and the material cross-sectional area of the hollow profile in the ratio of the modulus of elasticity of the material of the support body to the E Module of the concrete is selected. This is intended to ensure that the tensile stiffness of the transducer is equal to the tensile stiffness of the displaced concrete, so that the deformation properties in the area of the transducer are not changed and the flow of force through the transducer is not disturbed.
  • the strength and deformation properties of concrete change with time and stress.
  • the invention according to the claims now aims to detect strains in measurement objects with variable deformation behavior immediately after installation of the measuring device, for example in concrete that has not yet hardened, changes in the flow of force in the area surrounding the measuring device carrier that would distort the strains to be measured, switch off, and on the other hand to design the strain sensor so that pouring or injecting into concrete is possible without risk of damage and influences by corrosion or penetrating moisture cannot cause any noteworthy disturbance of the measurement results.
  • the object is achieved in that, on the one hand, the tensile stiffness of the support body is smaller than the product of the circumscribed envelope cross-sectional area with the modulus of elasticity of the measurement object and, on the other hand, in at least 2 transverse elements, the length measured transversely to the support body axis is greater than that in a transducer of the type mentioned three times the square root of the envelope cross-sectional area.
  • the tensile stiffness of the supporting body is therefore less than the tensile stiffness of the part of the test object lying in the area of influence of the measuring sensor.
  • the mean value of the expansion or compression of the supporting body represents the measured value directly, and not the detour via an "unobstructed" bend.
  • the two transverse elements according to the invention ensure that the measured strains originate from an area in the measurement object, the strains of which are not influenced by the supporting body of the transducer.
  • the combination of the rigid cross elements with a support body with low expansion stiffness prevents the cross elements from being punched into the concrete and thereby ensures that the elongation of the test object is forced onto the support body via the two cross elements.
  • the shape of the cross elements can be any, e.g. rod-shaped or plate-shaped. You only have to be dimensioned so large that they protrude into an area that is no longer influenced by the support body.
  • the support body is preferably designed as a hollow profile made of aluminum.
  • the support body is made of plastic, and it can be designed as a hollow or as a solid profile.
  • the deviation of the stress-strain line from the straight line is irrelevant, as long as no softening occurs in the area of the deformations to be measured, i.e. the slope of the stress-strain line retains its sign.
  • the required buckling stiffness (despite low elongation stiffness) can be achieved in a simple manner by inserting another profile made of rigid material, preferably steel, into the hollow profile, the total length of this profile being shorter than that of the Hollow profile of the support body is.
  • the additional profile prevents kinking, but because it is only pushed into the hollow profile (and not connected to it) and is shorter than this, it cannot influence the expansion or compression of the hollow profile.
  • the resulting cavity is filled with elastic foam, the compression of which is negligibly small in relation to the constraining force applied directly (axially) by the transverse elements.
  • strain gauges which are glued to the circumference in the middle in the longitudinal direction can be arranged on the latter.
  • the longitudinal expansion can also be determined by measuring the transverse expansion, whereby according to the invention, strain gauges which are glued to the circumference in the circumferential direction in the central region of the supporting body are arranged on the circumference.
  • the support body is designed as a hollow profile
  • a string for measuring deformations can be arranged in the hollow profile according to the principle of the vibrating string.
  • inductive displacement transducers for transmitting the expansion in the supporting body.
  • the invention is explained in more detail below with reference to an embodiment shown in the drawing.
  • the choice of the length of the support body 6 with a straight axis 14 depends on the measurement task; especially when measuring inhomogeneous materials, a sufficiently large measuring length is to ensure that the strain is averaged.
  • the firm connection of the soft support body 6 with the rigid cross elements 1 ensures that the support body 6 is only subjected to strains that originate from an area in the measurement object 13 which is not influenced by the measuring device.
  • a short bolt 3 is firmly connected to the cross bar 1.
  • the cross bar 1 can e.g. by gluing the shaft of the bolt 3 into the hollow profile of the supporting body 6.
  • a profile 4 the length of which is dimensioned such that a gap remains between the profile 4 and the bolts 3.
  • This profile 4 can also be covered with a plastic cover 5 to prevent thrust transmission on the circumference.
  • Strain gauges 7 are applied to the outside of the circumference in the longitudinal direction on the hollow profile of the support body 6. If the hollow profile of the support body 6 is made of aluminum, it will generally not have a constant transverse expansion factor over the entire measuring range, and therefore no strain gauges are attached transversely to the main direction of expansion. Strain gauges compensated for temperature characteristics can be used to compensate for undesired temperature influences. In the embodiment shown in the figure, compensation strain gauges 8 are additionally glued to a plate 9, which is made of the same material as the support body 6, with no non-positive connection to the support body 6. The strain gauges are advantageously connected in the form of a Wheatstone bridge.
  • the strain gauges and all electrical connections are to be protected against water ingress with suitable, permanently plastic covering material 10.
  • a strong plastic tube 11 which is pushed over the supporting body 6 and whose outer contour encloses a cross-sectional area 12, serves as protection against mechanical damage.
  • the remaining annular gap is preferably filled with silicone rubber 2 as additional protection against water ingress.
  • the measuring cable can be executed through this annular gap.

Abstract

Der erfindungsgemäße Meßwertaufnehmer zur Messung von Dehnungen von beispielsweise Beton oder Spritzbeton (13) besteht aus einem Tragkörper (6), dessen Dehnsteifigkeit geringer ist als die Dehnsteifigkeit des durch den Aufnehmer verdrängten Materialquerschnittes (12). An den beiden Enden des Tragkörpers (6) sind Querelemente (1) zur Krafteinleitung angeordnet. Durch die Kombination von relativ biegesteifen, ausreichend großen Querelementen (1) mit einem Tragkörper (6) mit der genannten, sehr geringen Dehnsteifigkeit wird sichergestellt, daß die Dehnungen im Beton (13) über die Querelemente (1) dem Tragkörper (6) ungestört und vollständig aufgezwungen werden und damit über die Dehungsmessung am Tragkörper (6) die Dehnung des Betons (13) direkt und unverzerrt gemessen wird. Der Tragkörper (6) ist zweckmäßigerweise als Hohlprofil aus Aluminium oder Kunststoff ausgebildet, in welches ein anderes Profil (4), z.B. aus Stahl, eingeschoben ist, um eine ausreichende Knicksteifigkeit zu erzielen.The transducer according to the invention for measuring strains of, for example, concrete or shotcrete (13) consists of a supporting body (6), the tensile stiffness of which is less than the tensile stiffness of the material cross-section (12) displaced by the transducer. At the two ends of the support body (6) transverse elements (1) are arranged for the introduction of force. The combination of relatively rigid, sufficiently large transverse elements (1) with a supporting body (6) with the very low elongation stiffness mentioned ensures that the expansion in the concrete (13) via the transverse elements (1) undisturbed and the supporting body (6) be forced completely and thus the strain of the concrete (13) is measured directly and undistorted via the strain measurement on the supporting body (6). The support body (6) is expediently designed as a hollow profile made of aluminum or plastic, into which another profile (4), e.g. made of steel, is inserted in order to achieve sufficient buckling rigidity.

Description

Die Erfindung betrifft einen Meßwertaufnehmer, bestehend aus einem durch die Deformation des ihn umgebenden Meßobjektes axial beanspruchbaren geraden Tragkörper und aus einer den Tragkörper umgebenden Hülle sowie aus mindestens 2 an den Tragkörpern ange­schlossenen steifen Querelementen.
In vielen Fällen wird Beton durch das Hooke'sche Gesetz be­schrieben. Diese Näherung ist in jenen Fällen vertretbar, in denen ein Betontragwerk nur geringen Spannungen im Verhältnis zur momentanen Druckfestigkeit ausgesetzt wird und der Bela­stungsbeginn relativ spät erfolgt. Bei frühzeitiger Belastung auf hohem Spannungsniveau muß hingegen das rheologische Mate­rialverhalten in der statischen Berechnung berücksichtigt werden.The invention relates to a transducer, consisting of a straight support body which can be axially stressed by the deformation of the measurement object surrounding it and of a casing surrounding the support body, and of at least 2 rigid transverse elements connected to the support bodies.
In many cases, concrete is described by Hooke's law. This approximation is justifiable in those cases in which a concrete structure is only subjected to low stresses in relation to the current compressive strength and the load starts relatively late. In the case of early stress at a high stress level, however, the rheological material behavior must be taken into account in the static calculation.

Es ist bekannt, daß unter bestimmten Bedingungen Beton ein ausgesprochen plastisches Verformungsverhalten zeigt und die zeitabhängigen Verformungen ein Vielfaches der sofort auftre­tenden elastischen ausmachen können. Dieser Umstand ist in gewissen Anwendungsfällen, beispielsweise bei der Bemessung von Spritzbetonschalen im Tunnelbau, von wesentlicher Bedeu­tung für das Ergebnis der Berechnung und somit für die Sicher­heit und die Wirtschaftlichkeit des Bauwerkes.
Aufgrund der Vielzahl sich beeinflussender Parameter müssen die getroffenen Rechenannahmen durch Messungen am Bauwerk überprüft werden. Dabei ist insbesondere die möglichst voll­ständige Erfassung der Dehnungen an ausgewählten Stellen von hoher Aussagekraft.
Es ist bereits bekannt, Dehnungsmeßgeber mit rohrförmigem Verformungskörper als Träger für Dehnungsmeßstreifen zur Mes­sung von Dehnungen in Bauwerken aus Beton zu verwenden. In der Regel weisen solche Aufnehmer eine höhere Dehnsteifigkeit als die von ihnen verdrängte Materialsäule auf, insbesondere bei Verwendung von Stahlrohren mit geringem Durchmesser. In diesem Falle wird eine verlustfreie Dehnungsübertragung vom Beton auf den Träger der Dehnungsmeßstreifen verhindert.It is known that, under certain conditions, concrete exhibits an extremely plastic deformation behavior and the time-dependent deformations can make up a multiple of the immediately occurring elastic ones. In certain applications, for example when dimensioning shotcrete shells in tunnel construction, this fact is of crucial importance for the result of the calculation and thus for the safety and economy of the structure.
Due to the large number of influencing parameters, the calculation assumptions made must be checked by measurements on the building. In particular, the most complete detection of the strains at selected points is particularly meaningful.
It is already known to use strain gauges with a tubular deformation body as a support for strain gauges for measuring strains in concrete structures. As a rule, such transducers have a higher stiffness than the material column they have displaced, especially when using steel tubes with a small diameter. In this case, lossless strain transfer from the concrete to the support of the strain gauges is prevented.

Es ist weiters aus der DE-PS 3 101 575 bekannt, daß Dehnungs­meßgeber mit einem Hohlprofil als Verformungskörper konstru­iert wurden, bei denen die durch die Außenkontur des Hohlpro­files definierte Querschnittsfläche und die Materialquer­schnittsfläche des Hohlprofiles im Verhältnis des E-Moduls des Materials des Tragkörpers zum E-Modul des Betons gewählt ist. Dadurch soll erreicht werden, daß die Dehnsteifigkeit des Aufnehmers gleich der Dehnsteifigkeit des verdrängten Betons ist, sodaß die Verformungseigenschaften im Bereich des Aufneh­mers nicht verändert werden und der Kraftfluß durch den Auf­nehmer nicht gestört wird.
Jedoch muß bei dieser Konstruktion bedacht werden, daß sich die Festigkeits- und Verformungseigenschaften von Beton in Abhängigkeit der Zeit und der Beanspruchung ändern. Es ist daher nur zu einem einzigen Zeitpunkt möglich, unverzerrte Meßwerte zu erhalten. Diese Konstruktion erlaubt also nicht, ab einem frühen Zeitpunkt zu messen und berücksichtigt nicht die zeitabhängigen Verformungskennwerte des Betons. Auch kön­nen Kriechdehnungen nicht verlustfrei erfaßt werden.
Es ist ferner aus DD-PS-141 710 bekannt, den Tragkörper aus einem gekrümmten Biegeblech, das sich in einer geraden Hülle befindet, zu bilden. In diesem Falle ist es für Messungen erforderlich, daß sich das Biegeblech unbehindert verkrümmen kann. Der dazu erforderliche seitliche Hohlraum bringt bei der Anwendung im Freien, insbesondere bei langlebigen Untertage­bauten oder unter rauhem Baustellenbetrieb die Gefahr mit sich, daß er sich mit Feuchtigkeit bzw. Wasser füllt. Die dadurch wachgerufene Langzeit-Korrosionsgefahr am dünnen Bie­geblech bzw. seiner Anschlüsse und die Gefahr der Behinderung der freien Verformbarkeit des Biegeblechs durch Eis- oder Sinterbildung im Laufe der Zeit bringt vor allem bei Langzeit­messungen außerhalb des Labors Unsicherheiten ohne Reparatur­möglichkeit mit sich.It is also known from DE-PS 3 101 575 that strain gauges were constructed with a hollow profile as a deformation body, in which the cross-sectional area defined by the outer contour of the hollow profile and the material cross-sectional area of the hollow profile in the ratio of the modulus of elasticity of the material of the support body to the E Module of the concrete is selected. This is intended to ensure that the tensile stiffness of the transducer is equal to the tensile stiffness of the displaced concrete, so that the deformation properties in the area of the transducer are not changed and the flow of force through the transducer is not disturbed.
However, it must be borne in mind with this construction that the strength and deformation properties of concrete change with time and stress. It is therefore only possible to obtain undistorted measured values at a single point in time. This design therefore does not allow measurements to be taken from an early point in time and does not take into account the time-dependent deformation characteristics of the concrete. Also, creep strains cannot be recorded without loss.
It is also known from DD-PS-141 710 to form the support body from a curved bending plate, which is located in a straight envelope. In this case, it is necessary for measurements that the bending plate can bend freely. The side cavity required for this entails the risk that it will be filled with moisture or water when used outdoors, particularly in long-lasting underground structures or under rough construction site operations. The resulting long-term risk of corrosion on the thin flexible sheet or its connections and the risk of the free deformability of the flexible sheet being prevented by ice or sinter formation over the course of time, particularly with long-term measurements outside the laboratory, entail uncertainties without the possibility of repair.

Hinsichtlich der Verwendung von Dehnungsaufnehmern mit gerin­gerer Dehnsteifigkeit als die der durch sie verdrängten Mate­rialsäule war bisher in der Fachwelt die Meinung vorherr­schend, daß aufgrund einer Beeinflussung des Kraftflusses im Bereich, in dem die Messung vorgenommen wird, nur entsprechend verzerrte Werte gemessen werden. Entgegen dieser Meinung soll die Erfindung die Verwendung eines solchen Dehnungsaufnehmers mit sehr geringer Dehnsteifigkeit ermöglichen.
Die Erfindung gemäß den Patentansprüchen zielt nun darauf ab, einerseits in Meßobjekten mit veränderlichem Verformungsver­halten Dehnungen schon sofort nach dem Meßgeräteeinbau, z.B. in noch nicht ausgehärtetem Beton, zu erfassen, dabei Änderun­gen des Kraftflusses im Umgebungsbereich des Meßgeräteträgers, die die zu messenden Dehnungen verfälschen würden, auszuschal­ten, und anderseits den Dehnungsaufnehmer so zu gestalten, daß ein Eingießen oder Einspritzen in Beton ohne Gefahr einer Beschädigung möglich ist und Einflüsse durch Korrosion oder eindringende Feuchtigkeit keine nennenswerte Störung der Meß­ergebnisse verursachen können.With regard to the use of strain transducers with a lower tensile stiffness than that of the material column displaced by them, the prevailing opinion in the professional world was that due to an influence on the force flow in the area in which the measurement is carried out, only correspondingly distorted values are measured. Contrary to this opinion, the invention is intended to enable the use of such an extensometer with very low elongation stiffness.
The invention according to the claims now aims to detect strains in measurement objects with variable deformation behavior immediately after installation of the measuring device, for example in concrete that has not yet hardened, changes in the flow of force in the area surrounding the measuring device carrier that would distort the strains to be measured, switch off, and on the other hand to design the strain sensor so that pouring or injecting into concrete is possible without risk of damage and influences by corrosion or penetrating moisture cannot cause any noteworthy disturbance of the measurement results.

Erfindungsgemäß wird die Aufgabe dadurch gelöst, daß bei einem Meßwertaufnehmer der eingangs genannten Art einerseits die Dehn­steifigkeit des Tragkörpers kleiner ist als das Produkt der um­schriebenen Hüllenquerschnittsfläche mit dem Elastizitätsmodul des Meßobjektes und daß anderseits bei zumindest 2 Querelementen deren quer zur Tragkörperachse gemessene Länge größer ist als das dreifache der Quadratwurzel aus der Hüllenquerschnittsfläche. Es ist also die Dehnsteifigkeit des Tragkörpers kleiner als die Dehnsteifigkeit des im Einflußbereich des Meßwertaufnehmers lie­genden Teiles des Meßobjektes. Der Mittelwert der Dehnung bzw. Stauchung des Tragkörpers stellt unmittelbar den Meßwert dar, und nicht der Umweg über eine "unbehinderte" Verbiegung.
Durch die beiden erfindungsgemäßen Querelemente wird gewähr­leistet, daß die gemessenen Dehnungen aus einem Bereich im Meßobjekt stammen, dessen Dehnungen nicht durch den Tragkörper des Meßwertaufnehmers beeinflußt werden. Durch die Kombination der biegesteifen Querelemente mit einem Tragkörper geringer Dehnsteifigkeit wird ein Einstanzen der Querelemente in den Beton verhindert und dadurch sichergestellt, daß die Dehnung des Meßobjektes über die beiden Querelemente dem Tragkörper aufgezwungen wird.According to the invention the object is achieved in that, on the one hand, the tensile stiffness of the support body is smaller than the product of the circumscribed envelope cross-sectional area with the modulus of elasticity of the measurement object and, on the other hand, in at least 2 transverse elements, the length measured transversely to the support body axis is greater than that in a transducer of the type mentioned three times the square root of the envelope cross-sectional area. The tensile stiffness of the supporting body is therefore less than the tensile stiffness of the part of the test object lying in the area of influence of the measuring sensor. The mean value of the expansion or compression of the supporting body represents the measured value directly, and not the detour via an "unobstructed" bend.
The two transverse elements according to the invention ensure that the measured strains originate from an area in the measurement object, the strains of which are not influenced by the supporting body of the transducer. The combination of the rigid cross elements with a support body with low expansion stiffness prevents the cross elements from being punched into the concrete and thereby ensures that the elongation of the test object is forced onto the support body via the two cross elements.

Die Form der Querelemente kann dabei beliebig sein, z.B. stab­förmig oder tellerförmig. Sie müssen lediglich so groß dimen­sioniert sein, daß sie in einen Bereich ragen, der durch den Tragkörper nicht mehr beeinflußt wird.The shape of the cross elements can be any, e.g. rod-shaped or plate-shaped. You only have to be dimensioned so large that they protrude into an area that is no longer influenced by the support body.

Vorzugsweise ist der Tragkörper als Hohlprofil aus Aluminium ausgebildet. Es ist jedoch erfindungsgemäß auch möglich, daß der Tragkörper aus Kunststoff ausgebildet ist, wobei er als Hohl- oder auch als Vollprofil ausgebildet sein kann. Die Abweichung der Spannungs-Dehnungslinie von der Geraden spielt dabei keine Rolle, solange im Bereich der zu messenden Verfor­mungen keine Entfestigung eintritt, also die Steigung der Spannungs-Dehnungslinie ihr Vorzeichen beibehält.The support body is preferably designed as a hollow profile made of aluminum. However, it is also possible according to the invention that the support body is made of plastic, and it can be designed as a hollow or as a solid profile. The deviation of the stress-strain line from the straight line is irrelevant, as long as no softening occurs in the area of the deformations to be measured, i.e. the slope of the stress-strain line retains its sign.

Wenn der Tragkörper als Hohlprofil ausgebildet ist, kann die erforderliche Knicksteifigkeit (trotz geringer Dehnsteifig­keit) auf einfache Weise dadurch erreicht werden, daß in das Hohlprofil ein anderes Profil aus biegesteifem Material, vor­zugsweise Stahl, eingeschoben wird, wobei die Gesamtlänge dieses Profiles kürzer als diejenige des Hohlprofiles des Tragkörpers ist. Das zusätzliche Profil verhindert das Knik­ken, kann aber, weil es in das Hohlprofil nur eingeschoben (und nicht mit ihm verbunden) ist und kürzer als dieses ist, die Dehnung oder Stauchung des Hohlprofils nicht beeinflussen. Der dabei entstehende Hohlraum wird mit elastischem Schaum­stoff gefüllt, dessen Stauchbehinderung im Verhältnis zur direkt (axial) von den Querelementen aufgebrachten Zwängungs­kraft verschwindend klein ist.If the support body is designed as a hollow profile, the required buckling stiffness (despite low elongation stiffness) can be achieved in a simple manner by inserting another profile made of rigid material, preferably steel, into the hollow profile, the total length of this profile being shorter than that of the Hollow profile of the support body is. The additional profile prevents kinking, but because it is only pushed into the hollow profile (and not connected to it) and is shorter than this, it cannot influence the expansion or compression of the hollow profile. The resulting cavity is filled with elastic foam, the compression of which is negligibly small in relation to the constraining force applied directly (axially) by the transverse elements.

Zur Übertragung der Dehnung des Tragkörpers können an diesem im mittleren Bereich in Längsrichtung am Umfang aufgeklebte Dehnungsmeßstreifen angeordnet sein. Bei Verwendung von Trag­körpern aus einem Kunststoff, der eine über den Meßbereich konstante Querdehnungszahl aufweist, kann die Längsdehnung auch über Messung der Querdehnung ermittelt werden, wobei erfindungsgemäß zur Übertragung der Dehnungen im mittleren Bereich des Tragkörpers in Umfangsrichtung am Umfang aufge­klebte Dehnungsmeßstreifen angeordnet sind.In order to transmit the elongation of the support body, strain gauges which are glued to the circumference in the middle in the longitudinal direction can be arranged on the latter. When using supporting bodies made of a plastic, which has a constant number of transverse strains over the measuring range, the longitudinal expansion can also be determined by measuring the transverse expansion, whereby according to the invention, strain gauges which are glued to the circumference in the circumferential direction in the central region of the supporting body are arranged on the circumference.

Wenn der Tragkörper als Hohlprofil ausgebildet ist, kann im Hohlprofil eine Saite zur Messung von Verformungen nach dem Prinzip der schwingenden Saite angeordnet sein. Schließlich ist es erfindungsgemäß auch möglich, zur Über­tragung der Dehnung im Tragkörper induktive Weggeber auzuord­nen.If the support body is designed as a hollow profile, a string for measuring deformations can be arranged in the hollow profile according to the principle of the vibrating string. Finally, according to the invention, it is also possible to arrange inductive displacement transducers for transmitting the expansion in the supporting body.

Die Erfindung wird nachfolgend an Hand eines in der Zeichnung dargestellten Ausführungsbeispieles näher erläutert. Die Wahl der Länge des Tragkörpers 6 mit gerader Achse 14 richtet sich nach der Meßaufgabe; besonders bei der Messung in inhomogenen Materialien soll durch eine ausreichend große Meßlänge eine Mittelwertbildung der Dehnung sichergestellt werden. Durch die feste Verbindung des weichen Tragkörpers 6 mit den biegestei­fen Querelementen 1 wird gewährleistet, daß dem Tragkörper 6 nur solche Dehnungen aufgezwungen werden, die aus einem Be­reich im Meßobjekt 13 stammen, der vom Meßgerät unbeeinflußt ist.The invention is explained in more detail below with reference to an embodiment shown in the drawing. The choice of the length of the support body 6 with a straight axis 14 depends on the measurement task; especially when measuring inhomogeneous materials, a sufficiently large measuring length is to ensure that the strain is averaged. The firm connection of the soft support body 6 with the rigid cross elements 1 ensures that the support body 6 is only subjected to strains that originate from an area in the measurement object 13 which is not influenced by the measuring device.

Um ein Knicken des Aufnehmers zu verhindern, wird in das Hohl­profil des Tragkörpers 6 ein anderes Profil 4 aus biegesteifem Material, vorzugsweise Stahl, geschoben, wobei eine Drucküber­tragung in Längsrichtung zu verhindern ist. Bei dem in der Figur dargestellten Ausführungsbeispiel ist ein kurzer Bolzen 3 mit dem Querbarren 1 fest verbunden. Der Querbarren 1 kann z.B. durch Einkleben des Schaftes des Bolzens 3 in das Hohl­profil des Tragkörpers 6 mit diesem verbunden werden. Zwi­schen den Bolzen 3 an den Enden des Hohlprofiles des Tragkör­pers 6 befindet sich ein Profil 4, dessen Länge so bemessen ist, daß zwischen dem Profil 4 und den Bolzen 3 ein Spalt freibleibt.In order to prevent the transducer from kinking, another profile 4 made of rigid material, preferably steel, is pushed into the hollow profile of the supporting body 6, pressure transmission in the longitudinal direction being prevented. In the embodiment shown in the figure, a short bolt 3 is firmly connected to the cross bar 1. The cross bar 1 can e.g. by gluing the shaft of the bolt 3 into the hollow profile of the supporting body 6. Between the bolts 3 at the ends of the hollow profile of the support body 6 there is a profile 4, the length of which is dimensioned such that a gap remains between the profile 4 and the bolts 3.

Dies ist notwendig, damit sich die Länge des Tragkörpers 6 ungehindert, entsprechend den vom Beton aufgezwungenen Verfor­mungen, ändern kann. Dieses Profil 4 kann auch noch mit einer Kunststoffhülle 5 überzogen werden, um die Schubübertragung am Umfang zu unterbinden.This is necessary so that the length of the supporting body 6 can change unhindered, in accordance with the deformations imposed by the concrete. This profile 4 can also be covered with a plastic cover 5 to prevent thrust transmission on the circumference.

Auf dem Hohlprofil des Tragkörpers 6 sind außen am Umfang in Längsrichtung Dehnungsmeßstreifen 7 appliziert. Wenn das Hohl­profil des Tragkörpers 6 aus Aluminium besteht, wird dieser in der Regel keine konstante Querdehnungszahl über den gesamten Meßbereich aufweisen, daher sind auch keine Dehnungsmeßstrei­fen quer zur Hauptdehnungsrichtung angebracht. Zur Kompensation unerwünschter Temperatureinflüsse können temperaturgangkompensierte Dehnungsmeßstreifen verwendet wer­den. Bei dem in der Fig. dargestellten Ausführungsbeispiel sind zusätzlich Kompensations-Dehnungsmeßstreifen 8 auf einem Plättchen 9, das aus dem gleichen Material wie der Tragkörper 6 besteht, aufgeklebt, wobei keine kraftschlüssige Verbindung mit dem Tragkörper 6 besteht. Die Dehnungsmeßstreifen werden zweckmäßigerweise in Form einer Wheatstone'schen Brücke ver­schaltet.Strain gauges 7 are applied to the outside of the circumference in the longitudinal direction on the hollow profile of the support body 6. If the hollow profile of the support body 6 is made of aluminum, it will generally not have a constant transverse expansion factor over the entire measuring range, and therefore no strain gauges are attached transversely to the main direction of expansion. Strain gauges compensated for temperature characteristics can be used to compensate for undesired temperature influences. In the embodiment shown in the figure, compensation strain gauges 8 are additionally glued to a plate 9, which is made of the same material as the support body 6, with no non-positive connection to the support body 6. The strain gauges are advantageously connected in the form of a Wheatstone bridge.

Die Dehnungsmeßstreifen sowie sämtliche elektrische Anschlüsse sind mit geeignetem, dauerplastischem Abdeckmaterial 10 gegen Wasserzutritte zu schützen. Als Schutz gegen mechanische Be­schädigung dient ein über den Tragkörper 6 geschobenes, star­kes Kunststoffrohr 11, dessen Außenkontur eine Querschnitts­fläche 12 umschließt. Der verbleibende Ringspalt ist vorzugs­weise mit Silikonkautschuk 2 als zusätzlichem Schutz gegen Wasserzutritte verfüllt. Die Ausführung des Meßkabels kann durch diesen Ringspalt erfolgen.The strain gauges and all electrical connections are to be protected against water ingress with suitable, permanently plastic covering material 10. A strong plastic tube 11, which is pushed over the supporting body 6 and whose outer contour encloses a cross-sectional area 12, serves as protection against mechanical damage. The remaining annular gap is preferably filled with silicone rubber 2 as additional protection against water ingress. The measuring cable can be executed through this annular gap.

Claims (8)

1. Meßwertaufnehmer, bestehend aus einem durch die Deformation des ihn umgebenden Meßobjektes axial beanspruchbaren gera­den Tragkörper und aus einer den Tragkörper umgebenden Hülle sowie aus mindestens 2 an den Tragkörpern angeschlos­senen steifen Querelementen, dadurch gekennzeichnet, daß einerseits die Dehnsteifigkeit des Tragkörpers (6) kleiner ist als das Produkt der umschriebenen Hüllenquerschnitts­fläche (12) mit dem Elastizitätsmodul des Meßobjektes (13) und daß anderseits bei zumindest 2 Querelementen (1) deren quer zur Tragkörperachse (14) gemessene Länge größer ist als das 3fache der Quadratwurzel aus der Hüllenquer­schnittsfläche (12).1. Transducer, consisting of a straight support body which can be axially stressed by the deformation of the measurement object surrounding it and of a casing surrounding the support body and of at least 2 rigid transverse elements connected to the support bodies, characterized in that on the one hand the tensile stiffness of the support body (6) is lower than the product of the circumscribed envelope cross-sectional area (12) with the modulus of elasticity of the measurement object (13) and that, on the other hand, with at least 2 transverse elements (1) whose length measured transversely to the support body axis (14) is greater than 3 times the square root of the envelope cross-sectional area (12). 2. Meßwertaufnehmer nach Anspruch 1, dadurch gekennzeichnet, daß der Tragkörper (6) als Hohlprofil aus Aluminium ausge­bildet ist.2. Sensor according to claim 1, characterized in that the support body (6) is designed as a hollow profile made of aluminum. 3. Meßwertaufnehmer nach Anspruch 1, dadurch gekennzeichnet, daß der Tragkörper aus Kunststoff ausgebildet ist.3. Sensor according to claim 1, characterized in that the support body is made of plastic. 4. Meßwertaufnehmer nach Anspruch 1 bis 3, dadurch gekenn­zeichnet, daß in das Hohlprofil des Tragkörpers (6) ein anderes Profil (4) aus biegesteifem Material, vorzugsweise Stahl, eingeschoben ist, wobei die Gesamtlänge dieses Pro­files (4) kürzer als das Hohlprofil des Tragkörpers (6) ist.4. Sensor according to claim 1 to 3, characterized in that in the hollow profile of the support body (6) another profile (4) made of rigid material, preferably steel, is inserted, the total length of this profile (4) shorter than the hollow profile of the Support body (6). 5. Meßwertaufnehmer nach Anspruch 1 bis 4, dadurch gekenn­zeichnet, daß zur Übertragung der Dehnung in an sich be­kannter Weise im mittleren Bereich des Tragkörpers (6) in Längsrichtung am Umfang aufgeklebte Dehnungsmeßstreifen (7) angeordnet sind.5. Sensor according to claim 1 to 4, characterized in that strain gauges (7) which are glued in the longitudinal direction on the circumference in the middle region of the supporting body (6) are arranged for transmitting the strain in a manner known per se. 6. Meßwertaufnehmer nach Anspruch 3, dadurch gekennzeichnet, daß zur Übertragung der Dehnungen im mittleren Bereich des Tragkörpers (6) in Umfangsrichtung am Umfang aufgeklebte Dehnungsmeßstreifen (7) angeordnet sind.6. Transducer according to claim 3, characterized in that strain gauges (7) which are glued on in the circumferential direction in the circumferential direction are arranged for transmitting the expansions in the central region of the support body (6). 7. Meßwertaufnehmer nach Anspruch 1 bis 3, dadurch gekenn­zeichnet, daß im Inneren des Tragkörpers (6) in an sich bekannter Weise zur Messung von Verformungen nach dem Prin­zip der schwingenden Saite eine Saite angeordnet ist.7. Transducer according to claim 1 to 3, characterized in that a string is arranged in the interior of the support body (6) in a manner known per se for measuring deformations according to the principle of the vibrating string. 8. Meßwertaufnehmer nach Anspruch 1 bis 3, dadurch gekenn­zeichnet, daß zur Übertragung der Dehnungen im Inneren des Tragkörpers (6) in an sich bekannter Weise induktive Wegge­ber angeordnet sind.8. Transducer according to claim 1 to 3, characterized in that inductive displacement sensors are arranged in a manner known per se for the transmission of the strains inside the support body (6).
EP87890054A 1986-03-20 1987-03-20 Measurement transducer Expired - Lifetime EP0239563B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT0074886A AT390515B (en) 1986-03-20 1986-03-20 MEASURING VALUE
AT748/86 1986-03-20

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EP0239563A1 true EP0239563A1 (en) 1987-09-30
EP0239563B1 EP0239563B1 (en) 1992-03-11

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EP87890054A Expired - Lifetime EP0239563B1 (en) 1986-03-20 1987-03-20 Measurement transducer

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US (1) US4730497A (en)
EP (1) EP0239563B1 (en)
JP (1) JPS62273423A (en)
AT (1) AT390515B (en)
BR (1) BR8701259A (en)
CA (1) CA1300400C (en)
DE (1) DE3777219D1 (en)
ES (1) ES2030762T3 (en)

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US5104390A (en) * 1988-09-01 1992-04-14 Alza Corporation Fluid receiving receptacle comprising biocide delivery system contacting outside of receptacle
DE4205624A1 (en) * 1992-02-25 1993-08-26 Hottinger Messtechnik Baldwin Deformation measuring device e.g. for testing concrete structure - has measurement spring of polymer concrete carrying measurement transducer, e.g. strain gauge, and with sealing coating
CN101710007B (en) * 2009-12-10 2011-03-16 陈新 Concrete wall body expansion internal stress measuring sensor and measuring method

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EP0260337B1 (en) * 1986-09-18 1989-06-28 Kistler Instrumente AG Force-measuring device with an electromagnetic transducer
US4908509A (en) * 1988-10-27 1990-03-13 Massachusetts Institute Of Technology Traction and reaction force microsensor
CA2015184C (en) * 1990-04-23 1993-12-21 Gerard Ballivy Method of instrumenting an already erected concrete structure and the so instrumented structure
US5846573A (en) * 1994-12-09 1998-12-08 Rjg Technologies, Inc. Mold core-pin deflection transducer
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FR2812940B1 (en) * 2000-08-11 2002-10-31 Freyssinet Int Stup METHOD OF MEASURING STRESS IN A CONSTRUCTION ELEMENT
EP2557390B1 (en) * 2011-08-12 2019-05-22 Hexagon Metrology S.p.A. Measuring machine provided with a block of concrete having the function of foundation or machine bed, and method for compensating the measuring errors due to deformations of the block
CH711008A1 (en) * 2015-04-30 2016-10-31 Kistler Holding Ag Contact force testing apparatus, use of such a contact force testing apparatus, and a method of manufacturing such a contact force testing apparatus.
US9989349B2 (en) * 2015-07-29 2018-06-05 Corebrace, Llc Displacement measurement systems and methods
CN107727569B (en) * 2017-09-30 2019-02-22 华北水利水电大学 A kind of test method for testing rock and concrete binding interface tensile strength
CN110685301B (en) * 2019-09-30 2020-09-25 西南交通大学 Arbitrary-appearance assembled test block for high and steep slope rock rolling test
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DE4205624A1 (en) * 1992-02-25 1993-08-26 Hottinger Messtechnik Baldwin Deformation measuring device e.g. for testing concrete structure - has measurement spring of polymer concrete carrying measurement transducer, e.g. strain gauge, and with sealing coating
CN101710007B (en) * 2009-12-10 2011-03-16 陈新 Concrete wall body expansion internal stress measuring sensor and measuring method

Also Published As

Publication number Publication date
DE3777219D1 (en) 1992-04-16
CA1300400C (en) 1992-05-12
JPS62273423A (en) 1987-11-27
US4730497A (en) 1988-03-15
ATA74886A (en) 1989-10-15
AT390515B (en) 1990-05-25
EP0239563B1 (en) 1992-03-11
ES2030762T3 (en) 1992-11-16
BR8701259A (en) 1987-12-29

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